dannydifalco

I have a 2001 maxima with 140k. One day it suddenly lost all power and would not idle. The only way to drive it would be to press the gas. I looked up the info here and found the problem seemed to be a bad gasket on the IACV that let coolant come inside and back feed to the ECM and fry it. So recently i replaced the IACV with an ebay special that had good feedback and i also pulled the computer and soldered in the new 509 chip and used a 30g wire to by pass a trace that was totally fried. Problem is I'm back at square one same problem occurs. Where should i start now? Do i buy a genuine IACV? Do i buy a TPS also? Do i replace the ECM?
The main question is should the car idle somewhat with a good IACV and a bad computer? Because that will at least tell me the IACV is good. Thanks!

This is the link to the valve i bought. http://www.ebay.com/itm/251145930015...84.m1439.l2649

ManualMaxima

iTrader: (10)

No the car won't idle well with a bad ECM no matter what, it controls the stepper motor within the IACV. To test the IACV you gotta pull it and bench test with a multimeter (looking for 22ohms across the appropriate pins found in the FSM). Since you used your original ECM and just soldered a new chip in you shouldn't have to do the idle relearn procedure but you might give it a shot.

dannydifalco

Well I'm trying to figure out what to go to next.
1. Do i have to replace the TPS sensor also? Will that contribute to it not idling properly?
2. The car still stalls and acts as if i did nothing to fix it. Can the car idle at all with a good IACV and a bad ECM?

Im trying to figure out if the ECM is bad and my soldering repairs didn't work or if i should try a genuine or different iacv.

ManualMaxima

iTrader: (10)

1. Many sources claim that you have to or should replace the TPS sensor. I checked mine with a multimeter per the FSM and did not replace it.

2. A car with a bad ECM / IACV will run fine, just not at idle (at all). What you will see is either stalling (yours) or wildly erratic up and down rpm changes. Like I said test the IACV for 22ohms resistance so you can rule it out or not. If it's good, you now know it's the ECM. Unfortunately there is really no other way to test unless you have access to some of the big money diagnostic equipment or a dealership/shop visit.

dannydifalco

Ok do you have ohms for the tps handy? And I'll test the iacv to see if it's good. Atleast I know now that even with a good iacv it can still not run and stall out.

TrueMaxima03

Could it be a bad MAF sensor?


I would disconnect the MAF sensor and trying starting it see what happens. If you disconnected the MAF and it runs better after, than you need a new MAF sensor. Something easy to rule out...

Emaximus

Dannydifalco,

How is that ICAV you bought off of eBay doing? I need to get one and was wondering how it was holding up. I love that price, I can get one for $167 with a year warranty though.

dannydifalco

I ended up returning that and getting one off of amazon for like $115 shipped. I also bought a tps sensor off of rockauto for $56 and then I got a used ecu off of eBay for $180 and had a locksmith come to my house and program the keys for $70. She runs like a champ now.

Emaximus

Nice, now I know I can just get a locksmith to reprogram keys if I need to get a new ecm. Any particular reason you returned the iacv? I just got one of eBay for $48 with a 6 month warranty (I know, I know, anyone can say warranty). But I actually went up to advance auto and the guy pulled an iacv out for me to look at and he leaned over and whispered, "there is no reason this thing is $200, I suggest you just get one online, that's where we get them." I love disgruntled, truth telling employees! I'll be doing this soon, hopefully my ecm isn't fried, but if it is I'll just send it off. And if that doesn't work, I'll find a nice used one. The dealership shall not get my hard earned money...

dannydifalco

No particular reason. I just wanted to make sure I had a quality valve especially one that was cut to spec so the gasket for perfectly so no more coolant leaks in and frys my new ecu.

Emaximus

Question for you. I checked my old IACV and it was at 23.1 ohms. I checked my new one and it was at 22 ohms. Is there really a difference between the two? If not then I bought a new valve for nothing, no big deal though as I can return it. But, I'm getting the p0505 code, so I'm guessing my ecm is toast more than likely? I may just keep the new valve and get my ecm fixed and be done with it, does that sound like a good plan of action? My Max is 15 years old and has been rock solid so I really can't complain too much.

greaseyoda

Hopefully this will help with your prob

DESCRIPTION




SYSTEM DESCRIPTION
This system automatically controls engine idle speed to a specified level. Idle speed is controlled through fine adjustment of the amount of air which by-passes the throttle valve via IACV-AAC valve. The IACV-AAC valve changes the opening of the air by-pass passage to control the amount of auxiliary air. This valve is actuated by a step motor built into the valve, which moves the valve in the axial direction in steps corresponding to the ECM output signals. One step of IACV-AAC valve movement causes the respective opening of the air by-pass passage. (i.e. when the step advances, the opening is enlarged.) The opening of the valve is varied to allow for optimum control of the engine idling speed. The crankshaft position sensor (POS) detects the actual engine speed and sends a signal to the ECM. The ECM then controls the step position of the IACV-AAC valve so that engine speed coincides with the target value memorized in ECM. The target engine speed is the lowest speed at which the engine can operate steadily. The optimum value stored in the ECM is determined by taking into consideration various engine conditions, such as during warm up, deceleration, and engine load (air conditioner, power steering and cooling fan operation).

COMPONENT DESCRIPTION




IACV-AAC Valve
The IACV-AAC valve is operated by a step motor for centralized control of auxiliary air supply. This motor has four winding phases and is actuated by the output signals of ECM which turns ON and OFF two windings each in sequence. Each time the IACV-AAC valve opens or closes to change the auxiliary air quantity, the ECM sends a pulse signal to the step motor. When no change in the auxiliary air quantity is needed, the ECM does not issue the pulse signal. A certain voltage signal is issued so that the valve remains at that particular opening.


Consult-II Reference Value In Data Monitor Mode


ON BOARD DIAGNOSIS LOGIC
Malfunction is detected when
(Malfunction A ) the IACV-AAC valve does not operate properly,
(Malfunction B ) the IACV-AAC valve does not operate properly.

Possible Cause

MALFUNCTION A

• Harness or connectors (The IACV-AAC valve circuit is open.)
• IACV-AAC valve

MALFUNCTION B

• Harness or connectors (The IACV-AAC valve circuit is shorted.)
• Air control valve (Power steering)
• IACV-AAC valve DTC Confirmation Procedure

NOTE:

• If "DTC Confirmation Procedure" has been previously conducted, always turn ignition switch "OFF " and wait at least 10 seconds before conducting the next test.
• Perform "PROCEDURE FOR MALFUNCTION A" first. If 1st trip DTC cannot be confirmed, perform "PROCEDURE FOR MALFUNCTION B".
• If the target idle speed is out of the specified value, perform "Idle Air Volume Learning" before conducting "DTC Confirmation Procedure". For the target idle speed, refer to the "Service Data and Specifications (SDS)".

PROCEDURE FOR MALFUNCTION A

TESTING CONDITION: Before performing the following procedure, confirm that battery voltage is more than 10.5 V with ignition switch "ON ".

WITH CONSULT-II

1. Turn ignition switch "ON ".

1. Select "DATA MONITOR" mode with CONSULT-II.
2. Start engine and let it idle.
3. keep engine speed at 2,500 rpm for three seconds then let it idle for three seconds . Do not rev engine to more than 3,000 rpm .
4. Perform step 4 once more.
5. If 1st trip DTC is detected, go to "Diagnostic Procedure" at the end of the article.

WITH GST
Follow the procedure "With CONSULT-II" above.

PROCEDURE FOR MALFUNCTION B

TESTING CONDITION:

• Before performing the following procedure, confirm that battery voltage is more than 11 V at idle.
• Always perform the test at a temperature above -10 °C (14 °F) .

WITH CONSULT-II

1. Open engine hood.
2. Start engine and warm it up to normal operating temperature.
3. Turn ignition switch "OFF " and wait at least 10 seconds .

1. Turn ignition switch "ON " again and select "DATA MONITOR" mode with CONSULT-II.
2. Start engine and run it for at least 1 minute at idle speed.
3. If 1st trip DTC is detected, go to "Diagnostic Procedure" below.

WITH GST
Follow the procedure "With CONSULT-II" above.

EC-AAC/V-01
EC-AAC/V-01 - Connector View
ECM Terminals And Reference Value
WIRING DIAGRAM

DIAGNOSTIC PROCEDURE
Diagnostic Procedure Steps 1 - 2
Diagnostic Procedure Steps 3 - 4
Diagnostic Procedure Steps 5 - 6
Diagnostic Procedure Steps 7 - 8
Diagnostic Procedure Steps 9 - 12

dannydifalco

I would just replace the valve anyway. It's possible that coolant leaked in through the bad gasket on valve and back fed and killed computer without blowing valve. Or your valve may be fine and maybe your electric motor mounts backfed and killed computer. I would pull computer and look at the 509 chip

cornholio

iTrader: (1)

mine ohmed about the same and passed all those other tests in the fsm. i replaced it and all my idle problems were fixed. i feel like that is a good sign that your ecm was spared, but it's pretty easy to pull the ecm and verify.

Emaximus

Thanks. I'll get it all put back together tomorrow and check the ecm. If it looks good, I'll crank her up. If ecm is toasted, off it goes to be repaired, I'm ready to have my Max back on the road.

maxiiiboy

You are jumping to conclusions.

It's dangerous to assume that you fixed your ECU by replacing the power transistor(s) - your ECU could have suffered other damage. I would also question your assumption that the new IACV (from eBay) is "good".

If it was my car, I would take the car to the dealer and pay them their standard diagnostic fee ($130 where I live) to confirm that the ECU is fine. Once the ECU sanity is confirmed, I would replace the IACV with an OEM part (try Courtesey parts).

Emaximus

Ok, I got everything back together and it seems to be running fine. Put the new valve in, no error codes, idling fine, etc. I've driven about 30 miles so far, hopefully it will hold. I did unplug my electronic motor mounts and my car is very quiet now. I didn't even realize I had a buzzing/whining noise and it rides just fine, no extra vibration or anything. None that I can tell anyway. I did not do the coolant bypass, but I am tempted to...

I did use an eBay valve for $50, so I'll post if it ends up failing anytime soon. I actually looked at the old valve and the new valve side by side and they look absolutely identical, number stamping and everything. We'll see how it goes. Thanks for all the input, it was a big help.